Cardiac myocyte-specific expression of inducible nitric oxide synthase protects against ischemia/reperfusion injury by preventing mitochondrial permeability transition.
BACKGROUND
Inducible nitric oxide synthase (iNOS) is an obligatory mediator of the late phase of ischemic preconditioning, but the mechanisms of its cardioprotective actions are unknown. In addition, it remains unclear whether sustained elevation of iNOS in myocytes provides chronic protection against ischemia/reperfusion injury.


RESULTS
Constitutive overexpression of iNOS in transgenic mice (alpha-myosin heavy chain promoter) did not induce contractile dysfunction and did not affect mitochondrial respiration or biogenesis, but it profoundly decreased infarct size in mice subjected to 30 minutes of coronary occlusion and 24 hours of reperfusion. In comparison with wild-type hearts, isolated iNOS-transgenic hearts subjected to ischemia for 30 minutes followed by 40 minutes of reperfusion displayed better contractile recovery, smaller infarct size, and less mitochondrial entrapment of 2-deoxy-[(3)H]-glucose. Reperfusion-induced loss of NAD(+) and mitochondrial release of cytochrome c were attenuated in iNOS-transgenic hearts, indicating reduced mitochondrial permeability transition. The NO donor NOC-22 prevented permeability transition in isolated mitochondria, and mitochondrial permeability transition-induced NAD(+) loss was decreased in wild-type but not iNOS-null mice treated with the NO donor diethylene triamine/NO 24 hours before ischemia and reperfusion ex vivo. iNOS-mediated cardioprotection was not abolished by atractyloside. Reperfusion-induced production of oxygen-derived free radicals (measured by electron paramagnetic resonance spectroscopy) was attenuated in iNOS-transgenic hearts and was increased in wild-type hearts treated with the mitochondrial permeability transition inhibitor cyclosporin A.


CONCLUSIONS
Cardiomyocyte-restricted expression of iNOS provides sustained cardioprotection. This cardioprotection is associated with a decrease in reperfusion-induced oxygen radicals and inhibition of mitochondrial swelling and permeability transition.
West
Matthew B
MB
Institute of Molecular Cardiology, University of Louisville, Louisville, KY, USA.
Rokosh
Gregg
G
Obal
Detlef
D
Velayutham
Murugesan
M
Xuan
Yu-Ting
YT
Hill
Bradford G
BG
Keith
Rachel J
RJ
Schrader
Jürgen
J
Guo
Yiru
Y
Conklin
Daniel J
DJ
Prabhu
Sumanth D
SD
Zweier
Jay L
JL
Bolli
Roberto
R
Bhatnagar
Aruni
A
D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D015971:Gene Expression Regulation, Enzymologic; D019157:Ischemic Preconditioning, Myocardial; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000503:physiopathology* / Q000517:prevention & control; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D052247:Nitric Oxide Synthase Type II / Q000235:genetics* / Q000378:metabolism*; D010477:Perfusion; D011073:Polyamines / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013096:Spermine / Q000031:analogs & derivatives / Q000494:pharmacology
D020030:Nitric Oxide Donors; D011073:Polyamines; D017382:Reactive Oxygen Species; C005391:diethylenetriamine; C091861:spermine nitric oxide complex; D013096:Spermine; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse